SV40 is being used to study malignant cell transformation and viral gene expression. The viral encoded large T antigen plays roles in both processes and is being studied with the aim of linking its known biological roles to its biochemical functions. Specifically we are investigating the ability of the protein to bind to DNA and to interact specifically with sequences at the origin of DNA replication on the viral genome. As T antigen is known to form rapidly-sedimenting complexes, to have ATPase activity and to bind to a 54000 mw host protein, these properties are also being studied, especially with respect to the DNA binding properties of the T antigen. We are attempting to isolate cellular DNA sequences in transformed cells for which active T antigen has specific affinity. SV40 RNA processing and translation is being studied in Xenopus Laevis oocytes. Viral DNA is microinjected into oocytes and subsequent modification of the RNA transcripts by capping, splicing and polyadenylation are analysed. We wish to study RNA processing in this system with the eventual aim of following these processes in developing Xenopus embryos.